Researchers can’t agree on whether we are sleep-deprived, writes Jay Rayner from London, but the evidence suggests that few of us get enough
IN their recent paper We are chronically sleep deprived, doctors Michael Bonnet and Donna Arand from Dayton, Ohio, produced facts and figures to support their title. They found that 50% of college students were suffering from serious or even pathological sleep deprivation.
In another survey, 82% of oil refinery shift workers stated they were sleep- deprived; 70% of train drivers questioned reported dozing off while driving their train. When the drivers were connected up by electrodes to a computer to test their claims, 36% were found simply to drop off at the controls.
American physician Dr Stanley Coren stated in a recent book that only if we took more than nine hours shuteye a night could we ever hope to function properly. Most studies show that we need between seven and eight hours sleep a night. Evidence suggests many aren’t getting it.
Oh dear. If this really is the case, then we’re in big trouble. The evidence of your own ears may already tell you that is the case. We have all had those muttered conversations about lack of sleep while standing around the office coffee machine, eagerly awaiting our caffeine fix.
Our own experience is one thing, expert opinion quite another. And at the moment expert opinion is deeply divided. “There is no substantive evidence to show that our daily amount of sleep has declined much over the course of history,” says Professor Jim Horne of Loughborough University, one of Britain’s leading academic sleep researchers.
Dr John Schneerson, director of the largest sleep clinic in the United Kingdom, disagrees. “Western society is getting more and more independent of its environment,” he says. “Artificial light is there to throw off our rhythms. A third of the population is in shift work. And then there are the social factors. Some shops stay open round the clock, life happens faster, there are always distractions like radio and TV to keep you awake.”
What neither Horne nor Schneerson disagree upon is the importance of sleep, although our knowledge of exactly why we need it is not complete. For small mammals it is clear that sleep provides the only real opportunity for the kind of rest necessary to repair muscle mass and conserve energy. Humans, however, can do that quite adequately by relaxing while awake.
For us it appears that sleep, which is governed by our circadian – or 24-hour – cycle, is important for our cognitive processes. Measuring brain waves using an electroencephalogram (EEG), it becomes clear that sleep falls into five stages, each of varying depths until we enter what is called Rapid Eye Movement or REM sleep, the period when we dream. REM sleep accounts for around 20 to 25% of the whole and occurs about every 90 minutes, each episode lasting 20 minutes. One popular theory is that REM sleep stimulates and tones up the brain so preparing it for wakefulness.
Jim Horne’s research at Loughborough has helped show that the part of the brain most affected by sleep deprivation is the pre- frontal area, which accounts for 30% of the mass and is responsible for helping us concentrate, for our working memory and our flexible thinking. If you deprive someone of sleep, their vocabulary will collapse and they will end up using clich after clich, which makes this tired and overworked journalist feel sick as a parrot.
The precise effects of extreme sleep deprivation in humans, however, are unknown. In one experiment using rats it was found that, after 14 days without sleep, they died. Sleep deprivation experiments with humans rarely go beyond three to five days for fear that something catastrophic might occur.
The only extended experiment on record involved Randy Gardner, an American schoolboy from San Francisco who announced in 1963 that he was going to try and stay up later than anybody in history. He managed 264 hours – a full 11 days – and right to the end still had periods of lucidity. He was able to play his pinball machine and often beat the sleep researchers who, after hearing of his world-record attempt, had flocked to observe him. Gardner still holds the world record. He suffered no ill effects from his experiment.
Jim Horne is not a man with much time for the anecdotal; as a scientist he is only concerned with the empirical and his data tells him that sleep deprivation is not a problem. “The acid test for sleep deprivation is daytime sleepiness,” he says. So, if you can find a way to measure daytime fatigue – the propensity to fall asleep, rather than a general tiredness that may come from strenuous work – then you can work out the level of deprivation. Researchers like Jim Horne are aided in their studies by the Multiple Sleep Latency Test, developed in the late Seventies.
During the test, subjects are asked to retire to a darkened room at regular intervals throughout a single day. They are then connected up to an EEG machine by electrodes, so that when they fall asleep it can be measured. According to the test, if you fall asleep within five minutes or less, you are suffering from pathological sleep deprivation. Up to 10 minutes or less and you are a borderline case. The average for a normal healthy person with no sleep problems is 12 to 15 minutes.
Horne had a theory: if we really are sleep- deprived, then if you take a sample of people who usually get the standard seven or eight hours and ask them to sleep longer than they normally would, they would get better test scores, indicating that they were less sleepy. And so a bunch of volunteers were invited to spend a week sparked out for 10 hours a night. Two majors results emerged. The first was that after the initial nights, extended sleep was often difficult to maintain. An extra two hours in bed generally resulted in only an extra hour of sleep. And secondly, the improvement in the test scores was only marginal.
“Perhaps sleep can be compared with eating and drinking,” Horne says. “A certain amount is vital but we can easily consume more than we really need. Just because we can, on days off, all sleep an hour or so longer than our average daily amount, it does not mean that we really need it.”
ENDS